Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$196.84	13.688%	$223.7835	$223.78	$223.80	$223.80
Purchase #2	$139.72	7.654%	$150.4142	$150.41	$150.40	$150.40
Purchase #3	$223.62	9.368%	$244.5687	$244.57	$244.55	$244.60
Purchase #4	$219.25	4.572%	$229.2741	$229.27	$229.25	$229.30
Purchase #5	$180.37	13.342%	$204.435	$204.44	$204.45	$204.40
Purchase #6	$20.32	3.860%	$21.1044	$21.10	$21.10	$21.10
Purchase #7	$87.46	13.460%	$99.2321	$99.23	$99.25	$99.20
7 purchase totals =	$1,067.58		$1,172.8120	$1,172.80	$1,172.80	$1,172.80